A more than two-mile stretch of road in southern Illinois will be closed for several weeks due to a yearly snake migration that is not often seen anywhere else in the country.
Known as "snake road," Forest Road #345 in the Shawnee National Forest was closed to vehicles starting Sept. 1 and continuing through Oct. 30, according to the U.S. Forest Service.
The road is shut down to vehicles twice a year, with another closure taking place from March to May.
The Illinois Department of Natural Resources says the twice-yearly event marks a time when snakes migrate to and from nearby limestone bluffs and the LaRue Swamp. IDNR notes that some of the snakes and amphibians making the trek from cliffs to water and back are endangered in Illinois and in the U.S., so the road closures help ensure their safety as they cross.
It's a rare and shockingly popular sight in southern Illinois, but while the road is closed to vehicles, it's not closed to people.
The forest service stresses to onlookers that "capturing, collecting or harassing wildlife of any kind is prohibited."
It's good advice not just for the snakes, but for humans, as a number of venomous species are part of the migration.
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According to Biologist Mark Vukovich, who spoke to NBC affiliate station 5 on Your Side, up to 23 species of snakes have been documented in the area. That includes the Northern Cottonmouth, Copperhead and Timber Rattlesnake species.
The forest service warns hikers of potential run-ins with venomous snakes as well.
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"Venomous snakes exist in the area, avoid being bitten by slowly moving away if you encounter any snake," a message on the department's website reads.
Vukovich said for those looking to witness the migration, the best viewing time will likely be in October.